1. Field of the Invention
The present invention relates to an inkjet printer.
2. Description of the Related Art
Conventionally, an inkjet printer for large format printing that includes a plurality of recording heads arrayed in a direction perpendicular to a scanning direction of a head unit is known. The inkjet printer having such a structure performs printing on a large area of a recording medium within a short time. Japanese Laid-Open Patent Publication No. 2013-67031 discloses an inkjet recording device including a plurality of head units arrayed in the scanning direction. The plurality of head units each include a plurality of recording heads arrayed in a feeding direction perpendicular to the scanning direction.
Some of recording mediums, such as cloth, paper and the like are not white. In the case in which process color ink is directly ejected onto such a non-white recording medium, the real color of the ink may not be provided. According to a technique for dealing with this situation, a recording head ejecting white ink is added to the printer described in Japanese Laid-Open Patent Publication No. 2013-67031. With this technique, first, a white ink layer is formed on the recording medium. After the white ink layer is formed on the recording medium, an image layer of process color ink is formed on the white ink layer. In this manner, a color close to the real color of the ink is able to be printed even on a recording medium that is not white.
Usually, the above-described technique provides a sufficiently high level of image quality even on a recording medium that is not white. However, a still higher level of image quality may be desired for some uses of the printed item. In the field of, for example, outdoor advertisements or the like, there is a need for an image providing a strong impression of having depth or massiveness in order to attract more attention. However, often, the conventional printing method does not fulfill such a need. A reason for this is that the image layer is thin and, thus, the influence of special color ink forming the underlying color layer is not completely eliminated. For example, in the case in which the special color ink is white ink, the image appears whitish and, thus, lacks massiveness. In order to deal with such a situation, the inventors of preferred embodiments of the present invention developed a method of printing an underlying color layer with a portion of an image being mixed in the underlying color layer. More specifically, according to this method, a portion of ink dots of process color ink used to form the image is extracted at a predetermined extraction ratio and printed concurrently with the underlying color layer, and then the image is printed to overlap the underlying color layer. The inventors of preferred embodiments of the present invention have discovered that the above-described method is able to provide a printed item appearing to be more massive than by conventional overlapping printing.
However, a printed item provided by the above-described method may involve the following problem. When the image is printed as being mixed in the underlying color layer (hereinafter, the image printed as being mixed in the underlying color layer will be referred to as an “underlying image”), a color of ink that is not conspicuous against the color of the underlying color layer is developed more weakly than the other colors of ink. As a result, the image in a finished state has a color balance different from that of the image according to the printing data (hereinafter, the image according to the printing data will be referred to as an “original image”).